Balance PvP is balanced around 8v8, with classes filling specific roles and a couple "jack of all trades" classes. Some classes excel at crowd control, which makes them difficult to deal with in the 4v4 arena environments where the balance gap widens considerably. One class in particular (Merc/Commando) has nearly always been behind the curve in PvP, and is virtually useless in 4v4 arenas.

Gameplay Yes, you can get by only doing PvP. That being said, you will level up much faster by doing PvE content, which does have an enjoyable story. Additionally, you will earn more credits and get free gear by doing PvE also. There is no PvP-specific gear until max level (65). There is virtually no OWPvP in SWTOR. You'll be able to gank on PvP servers to an extent, but if epic OWPvP battles are your thing, SWTOR is not for you. The main thing for PvP in this game is to remember that it's a team effort. You'll earn more credits, more XP, more ranking by playing objectives and winning the match versus worrying only about kills and individual stats.

Community The official SWTOR PvP forums are full of idiots and whiners who can't play. Consider yourself warned. Play whatever class you enjoy and just roll with it. They're all viable in casual play. If ranked PvP is your thing, then you'll typically need to prove your worth to a decent PvP guild. If you're a good player, they will find you.

PvP in this game can vary wildly depending on what time of day you queue up and/or who is on your team. Some days it seems like you can win a single match no matter what you do, and others it seems like you steamroll everything in sight. Your best bet at a good experience is to find a group to run with.